There is a very large number of important pharmaceutical products in the form of glycosides, which as a rule are effective only in this form, while their aglycons have lesser or different effects. Among the often used, medically effective glycosides are, for example, the cardioactive glycosides occurring in types of adonis, digitalis, nymphea, nerium, strophanthus, convallaria or urginea. It has long been known that such glycosidic active ingredients often have an improved or at least a more balanced effect if they are administered not in the pure form, but in the form of plant or animal extracts. From this it has been surmised that accompanying substances of natural material are most likely active as carriers; however, it has been very difficult or, in some cases impossible, up to now to determine exactly which substances are acting as carriers here. In any event, with isolated or artificially produced glycosides it has often been shown that the absorption ability is less in comparison with plant extracts, so that some of these glycosides cannot be used for therapy at all or only to a small extent. For example, it is known that in oral applications digitoxin is 100% absorbed, lanatoside A 70%, lanatoside C only 40%, G-strophanthin 2% and gitoxin not at all. In certain cases it has also been attempted to bypass the absorption through the gastro-intestinal tract and to take in the active ingredients through the skin. In those cases where the active ingredients are glycosides, absorption is as a rule insufficient, while with other active ingredients it often is quite good.
Surprisingly, it has now been determined that it is indeed possible to increase the transdermal absorption of glycosidic active ingredients, if the active ingredients are administered together with ethylene oxide adducts having approximately 20 to 30 ethylene oxide units of sterols or alcohols with approximately 12 to 30 C-atoms.
It could not be anticipated that it would be possible to dissolve the glycosides, which as a rule are hard to dissolve not only in water but as a rule even in lipophilic solvents, in an oil phase with the aid of solubilizer and to cause it to absorb transdermally from that phase, even if it is in the form of an emulsion, and this with much higher absorption than so far has been possible by the oral or transcutaneous route.